Unpatched Drupal Flaws Expose Sites to Attacks

The details of several vulnerabilities in the update process of the Drupal content management system (CMS) were disclosed on Wednesday by a security firm.

According to IOActive researcher Fernando Arnaboldi, one of the problems is related to the notifications Drupal shows for available updates. If there is a network problem, users are informed that their installation is up to date, even if it isn’t.

Arnaboldi said Drupal 6 displayed a warning message in case of network problems, but versions 7 and 8 erroneously tell users that the CMS is updated.

Users can check for updates manually by clicking the “Check manually” link available on the “Available updates” page. However, the expert determined that this link introduces a cross-site request forgery (CSRF) vulnerability that can be exploited to force website administrators to check for updates.

The vulnerability can also be exploited for server-side request forgery (SSRF) attacks against drupal.org. In these types of attacks, malicious actors can get targeted servers to consume bandwidth by tricking administrators into sending unlimited requests to updates.drupal.org. The issue does not impact Drupal 8, Arnaboldi said.

Another problem is that Drupal updates are downloaded unencrypted and their authenticity is not checked properly. A man-in-the-middle (MitM) attacker can exploit this vulnerability to serve a backdoored version of Drupal instead of a legitimate update. As Arnaboldi has demonstrated, an attacker can also modify the content of the “Available updates” page to increase the chances of the victim downloading the malicious update.

A malicious hacker could also deliver backdoored versions of Drupal modules to compromise a website. The attacker can intercept a module update request and serve a backdoored version of the component.

In his experiments, the IOActive researcher used this method to get a reverse shell on the targeted website. This would allow the attacker to execute arbitrary code and access the Drupal database password.

Drupal developers have been aware of this issue since 2012. Discussions regarding the flaw were reopened in November after Arnaboldi reported the other update process vulnerabilities.

Fixes are currently not available for any of the security holes. Until Drupal releases patches, users are advised to manually download updates for both Drupal itself and add-ons.

Experts often find vulnerabilities in Drupal and there have been cases where malicious actors started exploiting flaws within hours after patches were released. In October 2014, Drupal developers told webmasters that they should assume their Drupal 7 websites were compromised unless they patched immediately after an update was made available.

Eduard Kovacs is an international correspondent for SecurityWeek. He worked as a high school IT teacher for two years before starting a career in journalism as Softpedia’s security news reporter. Eduard holds a bachelor’s degree in industrial informatics and a master’s degree in computer techniques applied in electrical engineering.